Lamp-globe.



No. 639,687. Patented Dec. l9, I899.

- J. a. PENNYCUICK & r. w. BARRETT.

LAMP GLOBE.

(Application filed Jan. 19, 1899.)

(No Model.)

m: NORRIS FEYERS no. morcxurno, WASNXNGTON, D. c.

llNrTEn STATES PATENT OFFICE.

JAMES G. PENNYCUIOK AND FREDERIC W. BARRETT, OF TORONTO, CANADA.

LAM P-G LOBE;

SPECIFICATION forming part of Letters Patent No. 639,687, dated December '19, 1899 Application filed January 19, 1899 Serial No;702,738. (No model.)

To aZZ whom it may concern.-

Be it known that we, JAMES GRAY PENNY- CUIOK, sanitary engineer, and FREDERIO XVILLIAM BARRETT, lucical engineer, of the city of Toronto, in the county of York and Province of Ontario, Canada, have invented certain new and useful Improvements in Lamp-Globes, of which the following is a specification.

The object of our invention is to devise a globe or envelop for electric and other lamps which will so deflect the light from the lamp as to give an increased field of illumination and produce a cone of illumination of equal intensity at all points in any given plane at right angles to the axis of the cone; and it consists,essentially, in forming upon the globe a series of external prisms above and below a neutral line, the prisms above the neutral line being adapted to deflect incident rays from the center of illumination toward the horizontal and the prisms below the neutral line to deflect incident rays outwardly toward the horizontal, the whole being constructed in detail substantially as hereinafter more specifically described and then definitely claimed. a

The drawing represents a cross-section of one-half of a lamp-globe constructed in accordance with our invention.

Under ordinary circumstances a large percentage of the light-rays given off by a lamp travel upward and are lost in the airwithout in any way being effective for illuminating the ground or other surface beneath the lamp. There is also a zone or circle of intense light thrown downward in the immediate vicinity of the lamp, so that a small area receives an excessive amount of light, particularly in the case of a strong light like an electric-arc lamp, very dazzling to the eye, while at a distance the light soon becomes deficient. We obviate this difficulty by so constructing prisms at the upper portion of our globe that they will intercept the upwardly-traveling rays and deflect them downward, so that they will, after leaving the outer surface of the globe, travel in a direction slightly inclined below the plane of the source of light in the lamp. Further, by means of the prisms in the lower section of the globe we intercept the intense band of light traveling downward from the lamp and so refract and deflect it upward that a large proportion will, after leaving the outer surface of the globe, travel in a direction more nearly horizontal to the plane of'the source of light. The result of this double action in the upper and lower sections of the globe is to vastly increase the field of illumination of a lamp and to produce acorie of illumination of more equal intensity at all points in any given plane at right angles to the axis of the cone than is given by a bare light.

There is usually a circle below the lamp deficientin illumination owing to the shadows cast from its base. To illuminate this circle, we form at the bottom of the globe a series of prisms intended to divert the light incident upon them inward toward the vertical, so destroying the shadows.

Referring to the drawing, A represents the center of illumination, which may be taken as the average position of the arc in an electric-arc light.

B is the globe, having a series of annular prisms formed upon its outer surface. These prisms are formed in four sets 0, D, E, and

F. The upper sets of prisms are adapted to deflect the upwardly-traveling rays from the center of illumination and bend them downward toward the horizontal. With the extreme uppermost prisms 0 total internal reflection will occur, which effects the same result as the refraction occurring in the prisms D. The upper middle set of prisms D refract or divert the light incident thereon downward and outwardly in a direction more nearly horizontal than when emergent from the center of illumination. The set of prisms E refract the incident light-rays in an upward direction, so that they travel outwardly to a much greater distance than would be reached by the path taken by the downward rays. The set of prisms F are adapted to bend the rays of light incident thereon in toward the vertical, and thus illuminate the circle directly below the lamp. It will be noted that the retracting-surfaces a and a of each prism are, as far as possible, varied in angle according to their position with regard to the center of illumination, so that the light incident upon them may be directed to the proper place to send the greatest volume of light in the direction required and so produce the equality of illumination aimed at. It will further be noted that the inactive surfaces 1) of the prisms are set at such an angle that at any given point the surface of any given face is coincident or parallel with the path in the glass which the incident ray falling upon the prism from the center of illumination will take when deflected by the refractive effect of the glass in passing through it. In regard to said inactive surfaces 19 of the prisms just referredto we may state, further, that as soon as a ray of light strikes the curved inner surface of the globe its path is deflected,-and if the surfaces 1) were set at an angle to this path the light on striking the surfaces 1) would either be refracted or reflected, according to the angles at which they were set. It is therefore essential if these surfaces be inactive that they be parallel to the path of the ray of light through the glass of the globe at the point at which they are set. Thus these surfaces neither intercept nor divert any of the light from the source of illumination.

The globe is preferably circular in horizontal section, though polygonal or other forms might be adopted. In vertical section the globemay also be varied in shape to suit the source of illumination with which it is to be used.

It must be remembered that in all cases the internal surface of the globe forms one of the refract-ing sides of each prism, so that the curvature of the globe is such as to give with the angle of the outer refracting-surface of each prism the proper degree of refraction.

Although we use the words much more equal intensity, it would be correct to say equal intensity if the cone of illumination were made small and the prisms correctly calculated and distributed.

hat we claim as our invention is 1. A glass lamp globe or envelop having a series of external horizontal prisms formed thereon, each having at least two active surfaces, the angle between the active surfaces of the prisms beingvaried according to the position a particular prism may occupy with regard to the center of illumination and according to the curvature of the vertical section of the globe, the angles being arranged to produce a cone of illumination of much more equal intensity than is given by a bare light, substantially as and for the purpose specified.

2. A glass lamp globe or envelop having a series of external horizontal prisms formed thereon, each having at least two active surfaces and one neutral surface set at such an angle that it is coincident with or parallel to the path in the glass which. an incident ray falling on the prism from the center of illumination will take when deflected by the refractive eifect of the prism, the angle between the active surfaces of the prisms being varied according to the position a particular prism may occupy with regard to the center of illumination and according to the curvature of the vertical section of the globe, the angles being arranged to produce a cone of illumination of much more equal intensity than is given by a bare light, substantially as and for the purpose specified.

3. A glass lamp globe or envelop having a series of external horizontal prisms formed thereon in three sets, the upper set being adapted to deflect incident rays from the center of illumination toward the horizontal, the middle set to deflect incident rays outwardly toward the horizontal and the lower set to deflect incident rays down toward the vertical, so as to produce a cone of illumination of much more equal intensity at all points in any given plane at right angles to the axis of the cone than is given by a bare light, substantially as and for the purpose specified.

4. A glass lamp globe or envelop having a series of external horizontal prisms formed.

thereon above and below a neutral line, the prisms above the neutral line being adapted to deflect incident rays from the center of illumination toward the horizontal, and the prisms below the neutral line to deflect inci' dent rays outwardly toward the horizontal, each prism having one face coincident at any given point with a line parallel to the path of the glass which an incident ray will take when deflected by the refractive. effect of the glass prism, the angle between the active surfaces of the prisms being varied according to the position a particular prism may occupy with regard to the center of illumination and according to the curvature of the vertical, section of the globe, the angles being arranged to produce a cone of illumination of much more equal intensity than is given by a bare light, substantially as and for the purpose specified.

5. A glass lamp globe or envelop having. a series of external prisms formed thereon above and below a neutral line, the prisms above the neutral line being adapted to deflect incident rays from the center of illumination toward the horizontal, and the prisms below the neutral line to deflect incident rays toward the horizontal, the active surfaces of the prisms being varied in angle according to their position with regard to the centerof illumination, the effect of the varying prisms being to produce a cone of illumination of much more equal intensity at all points in any given plane at right angles to the axis of the cone than is given by a bare light, substantially as and for the purpose specified.

Toronto, Canada, January 9, 1899.

JAMES G. PENNYCUIOK. FREDERIC \V. BARRETT.

In presence of- JOHN G. RIDoUT, ,N. O. DICKSON. 

